PROJECT SUMMARY/ABSTRACT Alcohol misuse remains a major public health problem in emerging adults (age 18-25). Excessive drinking is the largest source of morbidity and mortality in this age group and also predicts subsequent alcohol problems across the lifespan. A large number of cross-sectional studies have found significant associations between alcohol misuse and indices from behavioral economics. Specifically, two novel behavioral economic domains - alcohol demand and proportionate alcohol-related reinforcement - have been consistently associated with alcohol misuse in emerging adults in cross-sectional and laboratory studies. These motivational measures may clarify the development of alcohol misuse, but no longitudinal studies have been conducted to date. The proposed study will use a longitudinal risk design to systematically investigate the relationship between these measures and changes in alcohol misuse in emerging adults. Specifically, the study will leverage these novel risk indicators to predict changes in drinking from age 22 to 25, a time period when many individuals `mature out' of alcohol misuse but others exhibit persistently high levels of problem drinking. To address this question, the study will assess 530 at-risk drinkers (50% male/50% female) every three months from 22 to 25 using in- person and Internet-based assessments. The study has two primary aims. The first primary aim is to predict changes in alcohol misuse in emerging adults using the novel behavioral economic measures - individually, in combination with one another, and in the context of established risk factors. The second primary aim is to examine mediating and moderating relationships. Mediational analyses will test whether the behavioral economic variables causally mediate the development of alcohol misuse over time or, alternatively, whether their influence is mediated by the established mechanisms. Moderator analyses will systematically examine differences based on college status (i.e., college vs. non-college) and other substance use. The study also has a secondary aim to inform future intervention studies. This exploratory aim is to identify the most salient periods of change and the concurrent psychosocial factors that increase or decrease the value of alcohol. Collectively, the study will leverage recent advances in behavioral economics to make major contributions to understanding of alcohol misuse over the transition to adulthood.